a big thanks to toops and Puddin' for proving the original information for this topic

Basic info:What are Power Discs?Power Discs are a supplement to your characters and gameplay in Disney Infinity. They are sold in blind packs of two and can be placed on your Infinity Base to enhance your game.What is the difference between Hexagonal and Circular pieces?Hexagonal pieces unlock assets to your toybox, such as a new dome/environment to have and create it or new mounts/vehicles to ride. These are placed on the hexagonal spot on the Infinity base.Circular pieces are character enhancements, such as enhanced attack power, movement speed, or increased money gain in play sets. These are placed underneath a figure on the base.

Rare Hexagonal DiscsDumbo the Flying Elephant - Adds the Dumbo ride from the Parks in the Toy BoxAbu the Elephant - Adds the elephant version of Abu in the Toy BoxAstro Blasters Space Cruiser - Adds the Astro Blaster vehicle from the Buzz Lightyear attraction in the Toy Box

Circular DiscsRalph’s Power of Destruction - (Wreck-It Ralph) - In-game character has a chance to deal extra damage.Dr. Doofinshmirtz’s Damage-Inator! - (Phineas and Ferb) - In-game character weapons have a chance to do more damage.Electro-Charge - (Frankenweenie) - In-game character has a chance to gain more health.Star Command Shied - (Toy Story) - In-game character has a chance to receive less damage.User Control – (Tron) - In-game character has a chance to gain experience at a faster rate.

Hexagonal DiscsPizza Planet Delivery Truck - (Toy Story) - (Mount) - Drive the Pizza Planet Truck from "Toy Story" inside the Toy Box.Maximus - (Tangled) - (Mount) - Ride Maximus from "Tangled" inside the Toy Box.Headless Horseman’s Horse - (Legend of Sleepy Hollow) - (Mount) -Ride the Headless Horseman's Horse inside the Toy Box.Flamingo Croquet Mallet - (Alice in Wonderland) - (Tool) - In-game character gets the Flamingo croquet mallet from "Alice in Wonderland" inside the Toy Box.Hangin’ Ten Stitch with Surfboard – (Lilo & Stitch) - (Mount) - In-game character gets a hover surfboard with Stitch on the front of it inside the Toy Box.Mike’s New Car – (Monsters University) - (Mount) - Drive Mike Wazowski's car inside the Toy Box.Frozen Flourish Texture Pack - (Frozen) - Make all of the terrain objects in the Toy Box themed to the "Frozen" film.Chill in the Air Skydome - (Frozen) - Make the sky in the Toy Box themed to the "Frozen" film.New Holland Skydome - (Frankenweenie) - Make the sky in the Toy Box themed to the "Frankenweenie" film.Victor’s Experiments Texture - (Frankenweenie) - Make all of the terrain objects in the Toy Box themed to the "Frankenweenie" film.Halloweentown Skydome - (Nightmare Before Christmas) - Make the sky in the Toy Box themed to the "Nightmare Before Christmas" film.Jack’s Scary Decorations Texture - (Nightmare Before Christmas) - Make all of the terrain objects in the Toy Box themed to the "Nightmare Before Christmas" film.

Rare Hexagonal DiscsElectric Mayhem Bus - (The Muppets) - (Mount) - Get on this ride to mayhem from your favorite muppet show.Condorman Glider - (Condorman) - (Pack) - If you like Condors and flying gracefully then this will be your favorite Power Disc.Hook’s Ship – (Peter Pan) - (Mount) - This vehicle is perfect for one-handed airborne pirates who like to cackle.

Circular DiscsMickey’s Sorcerer Hat - (Fantasia) – XP Boost - In-game character has a chance to gain experience at a faster rate.Violet’s Force Field – (The Incredibles) – Defense Boost - In-game character has a chance to receive less damage.Rapunzel’s Healing – (Tangled) – Health Regan - In-game character has a chance to gain more health. Chernabog’s Power – (Fantasia) – Damage Increaser - In-game character has a chance to increase all damage by 20%.

In this thread you will find all the possible Disney Infinity Power Disc Alchemy combinations.

Power Disc Alchemy is a feature that is a result of two power discs being used under your character creating a third effect. Not every combination yields an alchemy effect and two of the same disc never will yield a third, just double the effect of the disc which in most cases just doubles the chance of the effect taking place. Some effects are possible to create creating different discs (ex: Felix+Any economy boosting disc) and some are exclusive to specific characters (Ralph+Felix, Buzz+Zurg). A big thanks to Mycologist for putting together the initial list and sharing it with us to expand.

There are a couple that have two versions, such as Spark Shield and Improved Spark Shield. It is unknown for right now if it's better in terms of sparks earn or frequency of it happening.